Come Hell or High Water by
He doesn’t know what Dean’s thinking. This saving people thing, this hero complex, isn’t new, but it’s grown to disturbing levels. Sam doesn’t know where it’ll end, or with what, and at this point, he’s not sure what Dean’s intentions actually are: save as many innocents as he can, or get himself killed in the process. Dean's unravelling and Sam doesn't know how to fix it.